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Owning Palette: Control Charts VIs

Installed With: Statistical Process Control Toolkit

Computes points and limits for a u chart, a control chart for fraction of non-conformities or defects. Number of units inspected n can be constant for all c or vary for each element in c. Calculates both variable and constant chart limits. Optionally, you can choose a range of indices for samples to use and indices of samples to ignore in the control calculation. The actual number of samples the VI uses to calculate the control limits is also output. By default, control limits are calculated from the input samples. You can also calculate control limits from standard values by wiring the chart limit src input.

Details  

	chart limit src specifies whether or not to use standard values for the chart limit calculations. If unwired this defaults to the most common case where the chart limits are calculated from the data in the input array(s). You do not have to wire this cluster unless you want the chart limits to be calculated from standard values. When using standard values, the center line for the control chart, u-bar, is set to u0. source selects one of two sources for chart limits calculation: 0 from data—(Default) chart limits are calculated from the data in the input arrays as qualified by the index spec and indices to ignore inputs. 1 use std u0—chart limits are calculated from the standard value u0. std u0 is the standard u0 value to use when calculating chart limits from standard values. The center line for the control chart u-bar will then be set to u0.
	c:# defects/sample is the number of non-conformities or defects found for each number inspected.
	n: sample size (variable) is the number of units inspected for each value of c. Use this array if a variable number of units were inspected for each entry in c. The array length must be the same as the length of the array c.
	n: sample size (constant) is used if the same number of units was inspected for each entry in c. Otherwise, if you are providing an array for n, leave this input unwired.
	std error multiplier (3) is the multiplier to use for the upper and lower control limits. Normally you leave std error multiplier unwired, and the VI sets the control chart limits to ±3.0 standard errors. The default is 3.0.
	index spec is used to choose a range of samples in c to use for the control limit calculation. If you do not wire this cluster, all elements in c input array are included in the control limit calculation. start index is the index of the first element of c to include in the control limit calculation. Default is 0 or index of the first sample in the c array. end index is the index of the last element of c to include in the control limit calculation. Default is 0 which selects the last sample in the c array.
	indices to ignore is the indices of samples to exclude from the control limit calculation. Excluding samples is useful for eliminating out of control points from the control limit calculation. By default, this is an empty array.
	# samples in calc is the number of samples used in the control limits calculation.
	u: average # defects/unit is the number of defects divided by the number inspected. This is the average number of non-conformities or defects per unit inspected. This array is plotted on the u control chart.
	UCLu is the variable limit for the upper control limits. If std error multiplier is three, this output will be u-bar + 3 standard errors.
	LCLu is the variable limit for the lower control limits. If std error multiplier is three, this will be u-bar - 3 standard errors. The standard error calculation varies with n.
	u chart limits contains the constant limits for the u chart. average UCLu is the average value of the variable upper control limit for the u chart. If the number inspected is constant, use this for the upper control limit. u-bar is the estimated fraction of non-conformities or defects for the process if calculated from the input data. average LCLu is the average value of the variable lower control limit for the chart. If the number inspected is constant, use this for the lower control limit. standard error is the standard error associated with CLu.

u Chart Details

, if calculated from input data, otherwise